The present invention relates to methods and means for color detection and modification. It is particularly suited to color detection systems, color recognition systems, color modifications, and color creation systems.
In color detection systems the invention is particularly useful for the automatic mixing of paints, pigments and dyes, for the sorting of ripe fruit, grains and vegetables, and may also be used in robotic devices in combination with pattern recognition techniques in three-dimensional physical space.
In color modification systems it is particularly suited to the graphic arts industry wherein it may be used as an original graphics generator, in the preparation of four-color separation negatives, in the retouching of specific areas within a color image, and in the preparation of page composites.
In color recognition systems it is suited for geological and agricultural assessments, military reconnaissance, city planning and land use, and coastal oceanography.
In color creation systems it is particularly useful in modifying generated original graphics; in the television industry for modifying artwork and refining Chroma-key applications; in the modification of industrial audiovisual slides; and in computer-generated animation devices for the motion picture industry.
The invention as disclosed herein has both color detection and color modification phases. In addition, by virtue of the manner in which the colors are selected, mathematical mensuration of defined color information is easily derivable.
Historically, color analysis has been an extremely difficult and imprecise process. Color recognition devices generally fall into one of three categories, the first of which uses the wavelength of the light to isolate or detect a "pump" spectral color. While spectographic recognition or detection can be quite accurate with respect to such a pure color, it has a significant drawback. Pure wavelength differentiation does not take into account color differences that vary as a function of saturation or luminance. A textured article that is obliquely illuminated by a light source may have many variations in saturation and luminosity, and the color detected by a spectrograph will vary substantially. Spectrographic color detection or recognition is simply not capable of handling all of the differences caused by variations in saturation or luminosity.
A second method of handling color recognition is through the use of digital or analog threshold devices which work primarily at one value of luminance. The incoming colors are filtered to derive a two-axis or two-dimensional color pattern. The threshold devices are then gated to respond to a single color. An example of this type of device appears in U.S. Pat. No. 3,739,078 issued to Peter Pugsley, one of the present co-inventors, and Mouayed Dobouny on June 12, 1973.
A third type of color recognition device recognizes that color is, in fact, a three-dimensional subject. In U.S. Pat. No. 4,110,826 issued to Klaus Mollgaard et al, on Aug. 29, 1978, it is taught that color can be described by a three-dimensional model wherein the x and y axes represent chromaticity and the z axis represents luminance. This reference also teaches the use of coordinate transforms to alter the naturally-occurring shape of the defined color in order to assist in its detection. FIGS. 6A and 6B of the Mollgaard patent show that color values vary as a function of luminance and, in fact, two different colors may overlap on the x,y axis if two different values of luminance are considered.
The color detection circuitry used in the present invention is particularly suited to isolating and detecting colors in a three-dimensional environment. For example, an aerial reconnaissance photograph of a wheat field or a corn field will reveal a textured surface. If the agricultural crop were affected by blight or drought, the severity of the blight or drought could be determined by isolating the color signature of the blighted product and then scanning the entire image to determine the percentage of the image that contained that particular color signature. Prior at color recognition devices generally fail with textured surfaces because of the enormous number of combinations present when all possible values of hue, saturation and luminance are combined.
In addition to color detection, the present invention is equally applicable to color modification, wherein it is desired to modify one particular color within the image. U.S. Pat. No. 3,739,078 to Pugsley, discussed previously, and U.S. Pat. No. 2,799,722 to H. E. J. Neugebauer, both disclose methods of altering the color within a certain localized area of an image. In addition, there are many references, of which Pugsley's U.S. Pat. No. 3,893,166 is an example, which disclose the modification of a specific color component throughout the entire image. Localized color correction is highly useful in the graphic arts industry, wherein it is often desired to modify or retouch a specific image area. Again, prior art devices, when evaluating textured color or articles with three-dimensional modeling, have proved to be less than satisfactory in isolating the image area to be corrected. For example, a man's shirt pictured in a catalog may have been manufactured with a dye having a single set of values definable in terms of chromaticity but, because of variations in luminosity resulting from three-dimensional modeling of highlights and shadows, the values of chromaticity or a function of luminance or density may vary over a 20:1 ratio. Traditional methods of color detection would select certain color values of the shirt within the photograph but would miss others. Hence, it is customary in the graphic arts industry to employ expensive and time-consuming correction masks, or to hand etch various localized areas of the color-separation negatives, when color-retouching is required.
The present invention is also equally applicable to color generation. U.S. Pat. No. 4,183,046 to George W. Dalke, one of the co-inventors of the present application, and Michael D. Buchanan, which issued on Jan. 8, 1980, discloses a color generation system using digital techniques wherein intensity, hue and saturation can be varied independently, as desired.
The present invention, when combined with a color graphics system, enables the operator to independently vary luminance and color with respect to any given part of the image. This enables an artist to modify or create color in a truly electronic sense, and bypasses the requirement that the graphic image first be created in a tangible medium and then be reimaged with a video camera or the like.